In the United States, state and local authorities are in charge of
voting and the country uses more than a half dozen different voting technologies.
As a result, the country can't guarantee that it accurately counts national votes
in a timely fashion. This article discusses the problem and potential solutions to the U.S. voting dilemma.

You seem to be switching out the brilliant poll watchers (in the one envelope per vote per line case) with really careless poll watchers (in the case where a voter hacks into the voting machine to add a few million votes).

But even in the latter case, the fraud would be easy to detect, since each vote is represented by a physical scanned ballot that is (of course) kept by the machine, so one manual recount - or just comparing the number of ballots to number of votes in the machine - and the game is up.

And of course results of the one envelope per vote per line are almost certainly reported to the Secretary of State via electronic means, which is the logical place to insert a man-in-the-middle type attack to manipulate an election, regardless of the technology used by the voting booth.

Or just skip the voting booth altogether, as Lessadolla Sowers rather famously did.

The bottom line is that asking voters to wait in 37 lines, sorting through cards in each to find their candidate's to put in the envelope while being watched like a hawk by zealous poll watchers, is simply impractical in any urban area in the USA. And if they did, it's leaves just as many means (or more, actually) than an optical ballot scanner.